The invention relates to a punched part for producing an electrical resistor, in particular a current-measuring resistor. The invention relates further to a current sensor having such a punched part, and to a suitable production method.
It has already been known for a relatively long time to measure electric currents by the so-called four-conductor technique using a low-ohm current-measuring resistor (“shunt”). The electric current to be measured is thereby passed through the current-measuring resistor, the electric voltage drop across the current-measuring resistor being measured. The measured voltage is proportional to the current to be measured and thus constitutes a measure of the electric current.
It is known from EP 0 605 800 A1 to produce such a current-measuring resistor from a composite material strip 1, as is shown by way of example in FIG. 1. The composite material 1 accordingly consists of two strips 2, 3 made of a conductor material (e.g. copper) and a strip 4 made of a resistance material (e.g. CuMnNi alloy), the strip 4 made of the resistance material being arranged between the two strips 2, 3 of the conductor material and being welded to the strips 2, 3 of the conductor material along its longitudinal edges 5, 6. When the current-measuring resistors are produced from the composite material strip 1, punched parts are punched out of the composite material 1 transversely to the longitudinal direction of the strip, each punched part then forming a current-measuring resistor. The known punched parts according to EP 0 605 800 A1 accordingly have only two current connecting parts for passing the electric current in and out and a resistor element, which is arranged between the two current connecting parts in the direction of current flow and through which the electric current to be measured therefore flows.
Measurement of the electric voltage drop across the current-measuring resistor is generally carried out by means of an integrated circuit (ASIC: application specific integrated circuit), as is known, for example, from EP 1 363 131 A1. The integrated circuit used for measuring the voltage is generally connected to the current-measuring resistor by means of a printed circuit board via soldered connections, which leads to various disadvantages.
On the one hand, the integrated circuit and the current-measuring resistor are generally packaged separately in a housing, resulting in twice the outlay in terms of packaging.
On the other hand, the characteristics of the resistor and of the integrated circuit can only be matched in combination on the printed circuit board.
Furthermore, between the input stage of the input amplifier of the integrated circuit and the voltage tap of the current-measuring resistor, there are soldered connections, vias and conductor paths on the printed circuit board, which can lead to undesirable parasitic effects (e.g. thermovoltages, induction loops, crosstalk of other signals).
It is therefore desirable to integrate the current-measuring resistor and the integrated circuit for voltage measurement in a common housing. One possible approach is known from US 2010/0001382 A1, but this requires additional working steps which are not established in today's standard production methods.
In relation to the prior art, reference is further to be made to U.S. Pat. No. 5,534,788 A, DE 10 2006 039 722 A1, DE 10 2009 031 408 A1, DE 42 43 349 A1, DE 10 2011 113 002 A1 and DE 102 37 126 A1.
Finally, DE 601 28 510 T2 discloses a punched part having a landing area for provision with an integrated circuit. However, the punched part here consists of a uniform material and is therefore not suitable for a precision resistor. In a precision resistor, the actual resistor element on the one hand and the connecting parts on the other hand must consist of different materials. For example, the resistor element can consist of a copper-manganese-nickel alloy, while the connecting parts consist of copper or a copper alloy. The punched part according to DE 601 28 510 T2 is accordingly not suitable for a precision resistor.